Project #7 - Taming your Hawk .60
13,500 with pattern carb. and narrow blade 11-7 prop. 23,000 with large throat carb. and 9-7 racing type prop.
as well as attractive, the Hawk was Duke's first schnuerle ported
.60. Unusual features included a cylinder section made with integral steel fins and an ultra-hard piston made from low expansion aluminum. With an expansion rate comparable to that of iron, the piston could be fit much closer, however, it seems that, on some examples, this was pushed a bit too far. Although there was tremendous potential here, the Hawk also
exhibited a few problems that kept it from becoming as popular
as it could have been. The engine can be modified to overcome
these, however, the modifications are such that proper tools
and machining skills are required to accomplish them. For those
of you with the facilities, and skills, the following modifications
will allow your Hawk .60 to reveal it's true, and considerable,
There are two problems that must be taken care care of to smarten
up the Hawk. These are: excessive compression in general, and,
on some engines, an overly tight fit.
The Hawk was the first of numerous Fox engines over the years
in which the compression was, in our opinion, just too high for
friendly operation when using typical sport fuels (10-15% nitro).
Although Duke claimed the engine would run well on fuel containing
up to 25% nitro, we never found this to be true. Even on lower
nitro fuels, these engines could be inconsistent, very finicky
to adjust, run hot, and flameout unexpectedly. We found that
lowering the compression was the only way to cure this. The addition
of shims alone was not adequate, and machine work to the head
itself was also required. Material is removed in a cone-shaped
pattern as indicated by the shaded area in the diagram below.
Be warned that spare parts are no longer available if you
ruin the head. Proceed with care!
If you interested in having this modification done but cannot manage it yourself, we have a recommended
custom machine work..
(Click on picture for larger view)
This modification will eliminate about half of
the glow plug threads. After the modification, use short reach
Here's a picture of a stock and
In addition to the head modification,
you will require two head shims made from .010" stock. If
your flying site is at a high elevation and/or you keep the nitro
content below 10%, you may get away without the shims. You can
experiment a bit here.
The following quote from the Owners Manual will give you an idea
of what the problem is:
"In the interests of
good compression and long life we have fitted your Hawk as tight
as we dare. In the event yours is fit too close and you have
trouble with the piston seizing (engine stops abruptly on lean).....return
it to us and state your problem and we will hone it out at no
Since this engine has been out
of production for decades, it is unlikely that the offer from
Fox would still apply, free or otherwise. Of the two samples we have
in our personal collection one exhibited the seizing problem,
but we had the ability to hone it, which cured the problem.
If you also have this problem you will likely need to do the